Lamprecht SC, Crous PW, Groenewald JZ ... - IMA Fungus

Stenocarpella and Phaeocytostroma on maize
with differing vigour within each species. In spite of their
virulence, S. maydis is more commonly observed in the USA
(Latterell & Rossi 1983), as well as South Africa (Marasas et
al. 1979). Although commonly associated with root and stalk
rot of maize, not much is known about the pathogenicity of
P. ambiguum, other than the study by Stovold et al. (1996)
in Australia. Its potential role as primary pathogen was,
however, confirmed in the present study, though strains of
P. ambiguum generally appeared to be less virulent than the
strains of S. maydis tested (Tables 2, 3). Nevertheless, P.
ambiguum should be considered as an important pathogen of
maize, and certainly as part of a soilborne disease complex
could result in significant damage to maize plants. Surveys
conducted for a number of seasons in the KwaZulu-Natal
province showed that the incidences of both fungi increase
significantly towards the end of the growing season when
maize plants are often subjected to moisture stress (Results
not shown). Stovold et al. (1996) reported that while P.
ambiguum can cause extensive infection of maize roots the
fungus did not significantly affect the growth of plants under
optimal conditions of soil moisture and nutrition. Although
these fungi may overwinter in infected maize residue, from
where they infect the roots, mesocotyl, crown and eventually
the stalks of new plants, not much is known about their host
specificity, and whether they could also be isolated from
grasses that grow in the vicinity of maize fields.
Based on their pigmented conidia and Diplodia-like
morphology, both Stenocarpella and Phaeocytostroma
have in the past been suspected to be members of the
Boytyosphaeriaceae, being initially described in genera
such as Diplodia and Sphaeropsis. However, Crous et al.
(2006) revealed Stenocarpella to belong to the Diaporthales,
though the phylogenetic relationships of Phaeocytostroma
remained obscure until the present study. From the taxa
treated here (Figs 1, 2), it is clear that both anamorph genera
are best allocated to the Diaporthales, Diaporthaceae.
This is somewhat surprising, as their pigmented conidia
suggests that they might represent a separate family within
the Diaporthales. In spite of these differences, however, no
support could be obtained for polyphyly in Diaporthaceae.
These findings suggest that as observed earlier in the
Botryosphaeriaceae (Botryosphaeriales) (Crous et al. 2006,
Phillips et al. 2008), conidial pigmentation appears to be
uninformative at the family level, while conidiogenesis,
and the ability to produce both alpha and beta conidia,
appear more informative at family level in Diaporthaceae
(Diaporthales).
Acknowledgements
We thank the technical staff, Alta Schoeman, Almarie Van den Heever,
Thabo Phasoana, Sheryldene Williams, Gregory Anthony and John
Deysel (isolations, purifications and conducting the pathogenicity
test), Arien van Iperen (cultures), Marjan Vermaas (photographic
plates), and Mieke Starink-Willemse (DNA isolation, amplification
and sequencing) for their invaluable assistance.
REFERENCES
Barr ME (1978) The Diaporthales in North America. Mycological
Memoir 7: 1–232.
Bensch K, Groenewald JZ, Dijksterhuis J, Starink-Willemse M,
Andersen B, et al. (2010) Species and ecological diversity
within the Cladosporium cladosporioides complex
(Davidiellaceae, Capnodiales). Studies in Mycology 67:
1–94.
Cheewangkoon R, Crous PW, Hyde KD, Groenewald JZ, To-anan C
(2008) Species of Mycosphaerella and related anamorphs
on Eucalyptus leaves from Thailand. Persoonia 21: 77–91.
Crous PW, Phillips AJL, Baxter AP (2000) Phytopathogenic Fungi
from South Africa. Stellenbosch: University of Stellenbosch,
Department of Plant Pathology Press.
Crous PW, Slippers B, Wingfield MJ, Rheeder J, Marasas WFO, et al.
(2006) Phylogenetic lineages in the Botryosphaeriaceae.
Studies in Mycology 55: 235–253.
Crous PW, Verkley GJM, Groenewald JZ, Samson RA (eds) (2009)
Fungal Biodiversity. [CBS Laboratory Manual Series no.
1.] Utrecht: Centraalbureau voor Schimmelcultures.
Daniels BA (1983) Elimination of Fusarium moniliforme from corn
seed. Plant Disease 67: 609–611.
Fisher NL, Burgess LW, Toussoun TA, Nelson PE (1982) Carnation
leaves as a substrate and for preserving cultures of
Fusarium species. Phytopathology 72: 151–153.
Holliday P (1980) Fungus Disease of Tropical Crops. Cambridge:
Cambridge University Press.
Hoppe PE (1936) Intraspecific and interspecific aversion in Diplodia.
Journal of Agricultural Research 53: 671–680.
Kellerman TS, Prozesky L, Anitra Schultz R, Rabie CJ, et al. (1991)
Perinatal mortality in lambs of ewes exposed to cultures
of Diplodia maydis (= Stenocarpella maydis) during
gestation. Onderstepoort Journal of Veterinary Research
58: 297–308.
Kellerman TS, Rabie CJ, Westhuizen GCA van der, Kriek NP, Prozesky
L (1985) Induction of diplodiosis, a neuromycotoxicosis, in
domestic ruminants with cultures of indigenous and exotic
isolates of Diplodia maydis. Onderstepoort Journal of
Veterinary Research 52: 35–42.
Lamprecht SC (1986) A new disease of Medicago truncatula caused by
Cylindrocladium scoparium. Phytophylactica 16: 189–193.
Lamprecht SC, Farina MPW, Thibaud GR, Marais M, Habig JH,
Bloem JF, Swart A (2008) Soilborne diseases cause yield
depression of maize in South Africa. Journal of Plant
Pathology 90 (2, Suppl.): S2.412. (abstract).
Latterell, FM, Rossi AE (1983) Stenocarpella macrospora (= Diplodia
macrospora) and S. maydis (= D. maydis) compared as
pathogens of corn. Plant Disease 67: 725–729.
Lević J, Petrović T (1998) Formation of α- and β-conidia by
Phaeocytostroma ambiguum. Mycopathologia 140: 149–
155.
Marasas WFO, Renburg SJ van, Mirocha CJ (1979) Incidence of
Fusarium species and the mycotoxins, deoxynivalenol
and zearalenone, in corn produced in esophageal cancer
areas in Transkei, southern Africa. Journal of Agricultural
Food Chemistry 27: 1108–1112.
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